Apparatus for assembling small numbers of a large variety of different goods

ABSTRACT

An apparatus for and a method of assembling small numbers of a large variety of different products are disclosed. In order to eliminate stock of parts and prevent error in assembling inappropriate part, a straight pipe or rod is subjected to bending to a desired curved shape, and set to a predetermined position to assemble with the other parts, and then assembled.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for and a method ofassembling small numbers of a large variety of goods, such as goods withcurved elongated members like curved pipes or curved control rods.

Referring to FIG. 11(a), an automotive power steering gear assembly isdescribed as a typical example of the items of the above kind. Itcomprises a gear housing 1 with an integral power cylinder 2, and curvedpipes 3. Mounted within the gear housing 1 are a gear train of the rackand pinion type and a rotary valve. The curved pipes 3, which are formedby bending straight pipes, interconnect the gear housing 1 and the powercylinder 2 and serve as hydraulic fluid passages.

In the automobile assembly plants, small numbers of a large variety ofautomobiles are manufactured, and thus a large variety of differentpower steering gear assemblies are needed. Therefore, it has been theconventional practice to prepare a variety of different curved elongatedpipes by bending straight pipes, each having flared ends with nuts 3a asshown in FIG. 11(b), and store a considerably large quantity of them ata suitable storage location for adequate supply to the assembly line.Upon receipt of production instructions including a productspecification, an appropriate gear housing is connected to thecorresponding power cylinder in accordance with the productspecification. Then, an appropriate one of the curved pipes is selectedat the storage location, held at a right position relative to the gearhousing integral with the power cylinder, and secured thereto bytightening nuts at a predetermined torque.

Since small numbers of a large variety of different power steering gearassemblies are assembled and different curved pipes have to be prepared,a relatively large space is required at the storage location for thecurved pipes.

Besides, the appropriate one of the different curved pipes is manuallyselected so that there is the possibility of human error in making theselection.

Accordingly, an object of the present invention is to provide anapparatus for and a method of assembling small number of a large varietyof different products wherein the above-mentioned problems have beenalleviated.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an apparatus forassembling small numbers of a large variety of different products,comprising:

means for delivering a work piece to a predetermined position;

means for storing a variety of different straight elongated members;

means for selecting a predetermined straight elongated member out ofsaid variety of different straight elongated members in accordance witha production instruction;

means for bending said predetermined straight elongated member inaccordance with the production instruction to form a curved elongatedmember;

means for receiving said curved elongated member and holding the same ina predetermined position relative to said work piece; and

means for mounting said curved elongated member to said work piece.

According to another aspect of the present invention, there is provideda method of assembling small numbers of a large variety of differentproducts, comprising the steps of:

delivering a work piece to a predetermined position;

storing a variety of different straight elongated members;

selecting a predetermined straight elongated member out of said varietyof different straight elongated members in accordance with a productioninstruction;

bending said predetermined straight elongated member in accordance withthe production instruction to form a curved elongated member;

receiving said curved elongated member and holding the same in apredetermined position relative to said work piece; and

mounting said curved elongated member to said work piece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an apparatus according to the presentinvention which performs a method according to the present invention;

FIG. 2(a) is a top plan view of a pipe bender for bending an elongatedpipe;

FIG. 2(b) is a side elevation of the pipe bender;

FIG. 3(a) is a fragmentary front elevation, partly sectioned, of a pipeset robot which receives a curved pipe and holds the same relative to awork, and shows a hand of the robot;

FIG. 3(b) is a side elevation of the hand of the pipe set robot;

FIG. 4(a) is a fragmentary front elevation, partly sectioned, of a nuttightening robot and shows a hand of the nut tightening robot;

FIG. 4(b) is a side elevation of the hand of the nut tightening robot;

FIG. 5(a) is a longitudinal section of an open end air wrench;

FIG. 5(b) is a fragmentary view, partly sectioned, of the open end airwrench as viewed from the bottom in FIG. 5(a);

FIG. 6 is a plan view, partly sectioned, of a torque wrench;

FIG. 7 is an air pressure circuit for activation of the hand of the pipeset robot and the open end air wrench;

FIG. 8 is a block diagram of a control unit for the nut tighteningrobot;

FIG. 9 is a flow diagram of a control program for activating theapparatus shown in FIG. 1;

FIG. 10 is a flow diagram of a control program for tightening nut withthe open end air wrench and the torque wrench;

FIG. 11(a) is a perspective view of a power steering gear assemblydiscussed before as a typical example of products;

FIG. 11(b) is a section of a portion of the power steering gearassembly, showing connection between a flared end of the pipe and thepower cylinder; and

FIG. 12 is a perspective view of a master cylinder as another typicalexample of the products.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the accompanying drawings, and particularly to FIG. 1, anapparatus according to the present invention comprises a numericallycontrolled (NC) pipe bender 11, a pipe set robot 31, and a nuttightening robot 51.

Referring to FIGS. 2(a) and 2(b), the NC pipe bender 11 comprises aslide table 12 with a mobile carrier 14 thereon. The mobile carrier 14rotatably supports a chuck 13, and has mounted thereon a torque motor 15for rotating the chuck 13. The mobile carrier 14 is guided in such amanner that it can slide in the longitudinal direction of the table 12in response to rotation of a feed motor 16 mounted on the table 12 onthe righthand end, as viewed in FIGS. 2(a) and 2(b).

Mounted on the lefthand end, as viewed in FIG. 2(a) and 2(b), of thetable 12 are a bending roll 17 with an outer peripheral groove 17ahaving a semicircular cross sectional profile, and a clamp 18 with asemicircular groove opposed to the groove 17a of the bending roll 17.The bending roll 17 and the clamp 18 are rotatable by a drive mechanism,not shown, about an axis of rotation of the bending roll 17.

Also mounted on the lefthand end, as viewed in FIG. 2(a), is a pressuredie 19 with a semicircular groove opposed to the groove 17a of thebending roll 17. The pressure die 19 is guided to move in thelongitudinal direction of the table 12 and it is activated to movetoward or away the bending roll 17.

Referring back to FIG. 1, this pipe bender 11 comprises a microcomputerbased control unit 20, and a pipe loader 21. The control unit 20controls actions of the above-mentioned mechanisms and the pipe loader21 in accordance with instructions contained in control program storedin a memory of the microcomputer.

The pipe loader 21 comprises a chute 22 including four trays storingfour different groups of straight pipes 3, respectively. Each of thepipes 3 has flared ends with flare nuts 3a thereon, see FIG. 11(b).Straight pipes 3 of four different lengths are prepared and divided intofour groups and stored in different trays of the chute 22. The pipeloader 21 also comprises a chain conveyer 23, and a hand 24. Among all,an appropriate straight pipe 3 is selected and supplied to the chainconveyer 23 by means of a stopper mechanism, not shown. The conveyer 23lifts the straight pipe 3 supplied up to a predetermined position wherethe hand 24 grips the pipe 3. After having gripped the pipe 3, the hand24 brings it to a predetermined position above the slide table 12.

With the NC pipe bender 11, if the control unit 20 is instructed withthe specification of a gear power steering gear assembly and the bendingprocess of a pipe 3, the stopper mechanism of the pipe loader 21supplies a straight pipe 3 having a length corresponding to thespecification given to the chain conveyer 23 from the chute 22. Thechain conveyer 23 delivers this pipe 3 to the hand 24. Then, the hand 24holds this pipe 3 at the predetermined position above the slide table24.

Thereafter, the chuck 13 moves toward the bending roll 17 to hold theadjacent end of the pipe 3, and further moves in the same directionuntil that portion of the pipe 3 which is to be subjected to the bendingis disposed between the bending roll 17 and clamp 18.

Then, the clamp 18 moves toward the bending roll 17 until the pipe 3 isinterposed between the groove of the clamp 18 and the outer peripheralgroove 17a of the roll 17, while the pressure die 19 moves toward thebending roll 17 and it receives the pipe 3 in its groove to support thesame. With this state being kept, the roll 17 and clamp 18 rotate, whilethe chuck 13 moves without any resistance in accordance with thisrotation. In this process, the pressure die 19 holds the pipe 3 in theouter peripheral groove 17a of the bending roll 17 and thus the pipe 3is bent to a predetermined curvature. The clamp 18 and pressure die 19move back away from the bending roll 17, and the roll 17 and clamp 18rotate back. Then, the chuck 13 moves towards the roll again untilanother portion of the pipe 3 which is to be subjected to the bendingprocess is disposed between the bending roll 17 and clamp 18. Duringthis movement, the chuck 13 may be turned through a predetermined angleif desired. Then, the above-mentioned bending process is repeated.

The straight pipe 3 has predetermined portion or portions bent to make apredetermined curved pipe corresponding to the specification given.

The pipe set robot 31 is disposed between a conveyer 42 and the NC pipebender 11. A work piece, namely, an integral unit of a gear housing 1integral with a power cylinder 2, is placed on a pallet 41. The pallet41 is delivered by the conveyer 42 to a predetermined position relativeto the pipe set robot 31. The pipe set robot 31 includes a hand 32 thatis illustrated in FIGS. 3(a) and 3(b).

Referring to FIG. 3(a), the hand 32 has a pair of claws 33 with fingers34, respectively. The claws 33 are movable toward each other by an aircylinder, not shown. The hand 32 therefore can hold the pipe 3 betweenthe fingers 34 when the claws 33 are moved toward each other.

The pipe set robot 31 is controlled by a control unit, not shown. Uponcompletion of the bending process by the NC pipe bender 11, theabove-mentioned hand 32 holds the curved pipe 3 and then the chuck 13releases the pipe 3 and moves back to the waiting position. Then, thepipe set robot 21 moves the hand 32 with the curved pipe 3 interposedbetween the fingers 34 to a predetermined position relative to the gearhousing 1 integral with the power cylinder 2, keeping it at thispredetermined position.

The nut tightening robot 51 is opposed to the pipe set robot 31 acrossthe conveyer 42, and includes a generally C-shaped bracket 52, as ahand, as illustrated in FIGS. 4(a) and 4(b).

Referring to FIGS. 4(a) and 4(b), the bracket 52 has a clamp 55 slidablymounted thereon by four guide shafts 53 and a ball type bushing 54.Springs 56 are arranged between one arm of the bracket 52 and the clamp55 to bias the clamp 55 downwadly, as viewed in FIG. 4(a). The guideshafts 53, bushing 54 and springs 56 constitute an equalizer.

As best seen in FIG. 4(b), the clamp 55 supports the open end air wrench611 and the torque wrench 81 in such a manner that they extend in theopposite directions from the bracket 52.

Referring to FIG. 5(a), the open end air wrench 61 includes an airoperated motor 62 with a reduction gear box. The output shaft 62a of theair motor 62 is fixedly coupled with a bevel gear 63 which meshes withanother bevel gear 64 integral with a pinion 65. As best seen in FIG.5(b), the pinion 65 meshes with a gear 66 which in turn meshes with agear 67. The gear 67 meshes with two pinions 68 and 69 which in turnmeshes with an external gear 70a formed around the outer periphery of asocket 70. The arrangement is such that if the pinion 65 rotatescounterclockwise, as viewed in FIG. 5(b), the socket 70 rotatescounterclockwise; and if it rotates clockwise, the socket 70 rotatesclockwise. The socket 70 includes a hexagonal portion 70b and a bottomwall 70c, and it is formed with a cutout or opening 70d.

The open end air wrench 61 includes a ratchet 71 and a rotary encoder72. The ratchet 71 is arranged such that when the socket 70 rotates in adirection opposite to a direction in which the nut is tightened, itengages with the gear 67 and stops this rotation of the socket 70 whensocket 70 comes to a receptive position where the opening 70d faces tothe left as viewed in FIG. 5(b). The rotary encoder 72 measures an angleof rotation of the bevel gear 64 and thus an angle of rotation of thesocket 70.

With the open end air wrench 61, when air pressure is supplied to oneport, the output shaft 62a rotates clockwise as viewed from the left inFIG. 5(a). This clockwise rotation of the output shaft 62a istransmitted via the gears 63 to 69 to the socket 70, causing the socket70 to rotate in the nut tightening direction, namely in counterclockwisedirection as viewed in FIG. 5(b). Since the output shaft 62a rotatescontinuously, the socket 70 rotates continuously in the nut tighteningdirection. When air pressure is supplied to the other port of the airmotor 62, the output shaft 62a rotates in the opposite direction andthus the socket 70 tends to rotate in the opposite direction. Since thegears 67 and 70a are substantially identical to each other, the reverserotation of the socket 70 is stopped at the central receptive positionas illustrated in FIG. 5(b) because the ratchet 70 engages with the gear67 before the gear 67 make a full turn during its reverse rotation.

Referring to FIG. 6, the torque wrench 81 includes a tube 82 with anopen end, and a spanner-like head 83. The head 83 is formed with theopposed spaced parallel sides 83a and is pivotably mounted via a headpin 84 on the tube 82 at a portion adjacent the open end thereof. Thespanner-like head 83 extends into the tube 82 has an inner end connectedvia an inclined link 85 to the adjacent end of a thruster 86 slidablydisposed in the tube 82. The inclined link 85 is inclined relative tothe axis of the tube 82. A spring 88 is operatively disposed between thethruster 86 and a thrust ring 87. The thrust ring 87 is threadedlyengaged in the tube 82 and adjustable in axial direction relative to thetube 82. Mounted on the outer periphery of the tube 82 is a limit switch89 which is so constructed and arranged as to detect rotation of thehead 83 beyond a predetermined angle. With the nut interposed betweenthe opposed two spaced parallel sides 83a, if the tube 82 is rotatedabout the central axis of the nut. a moment about the head pin 84 isimparted to the head 83, biasing the thruster 86 via the link 85. If thebiasing force exceeds the preloaded pressure applied to the spring 88,the head 83 begins to rotate about the head pin 84, thus activating thelimit switch 89.

Therefore, with this torque wrench 81, the limit switch 89 is activatedto produce an output signal when the torque applied to the nut exceedsthe predetermined torque. This predetermined torque is adjustable byadjusting the position of the thrust ring 87 to modulate the preloadedpressure of the spring 88.

The supply of air pressure to the air cylinder of the hand 32 and to theopen end air wrench 61 is controlled by an air pressure circuit shown inFIG. 7.

This air pressure circuit comprises a source of air pressure 91, and apressure reduction valve 92. The air pressure generated by the pressurereduction valve 92 is supplied on one hand to a solenoid operatedselector valve 95 via a pressure line 93, and on the other hand to asolenoid operated selector valve 96 via a pressure line 94. The solenoidoperated selector valve 95 is connected to both chambers of the aircylinder of the double action type of the hand 32, respectively, and ithas five ports and three positions. The other solenoid operated selectorvalve 96, which has a function to acivate or stop the action of the openend air wrench, has five ports and two positions and it is connected toa solenoid operated selector valve 97. The solenoid operated selectorvalve 97 has five ports and three positions, and it has an outlet portconnected to a pressure line 98 and other outlet port connected to aanother pressure line 99. The pressure line 98 is connected to asolenoid operated selector valve 100 having five ports and twopositions. The solenoid operated selector valve 100 has a function toselect low speed rotation of air motor 62 or high speed rotationthereof, and it has an outlet port connected to an air pressure line 101and another outlet port connected to an air pressure line 102. The airpressure line 101 is connected via a one-way check valve 103 to a portinducing positive rotation of the air motor 62 of the air wrench 61,while the another pressure line 102 is connected via a pressurereduction valve 104 and a thorttle valve 105 to a port inducting reverserotation of the air motor 62 of the air wrench 61.

In this air pressure circuit, the pressure reduction valve 92 regulatedair pressure discharged from the source of pressure 91 to generate abase pressure. This base pressure is delivered to the pressure lines 93and 94. In response to the position taken by the solenoid operatedselector valve 95, the base pressure is supplied selectively to one orthe other chamber of the air cylinder of the hand 32, causing thefingers 34 to move toward each other or away from each other. If thesolenoid operated selector valve 96 is activated, the supply of basepressure to the solenoid operated selector valve 97 is permitted orinterrupted in response to the position taken by the solenoid operatedselector valve 96. If the solenoid operated selector valve 97 isactivated, the base pressure supplied thereto is supplied selectively tothe pressure line 98 or the pressure line 99.

The base pressure supplied to the pressure line 98 is further suppliedselectively to the pressure line 101 or the pressure line 102 under thecontrol of the solenoid operated selector valve 100. The base pressureadmitted to the pressure line 101 is supplied via the one-way checkvalve 103 to the port inducing the forward rotation of the air motor 62,causing the air motor 62 and thus socket 70 to rotate in the forwarddirection at a high speed. On the other hand, the base pressure admittedto the pressure line 102 is supplied to the pressure reduction valve 104where the pressure reduction is effected and the reduced air pressure issupplied via the throttle valve 105 to the port inducing the reverserotation of the air motor 62, causing the air motor 62 and thus thesocket 70 to rotate in the positive direction at a low speed. The basepressure admitted to the pressure line 99 is subjected to pressurereduction at the pressure reduction valve 106 and supplied via thethrottle valve 107 to the port inducing the reverse rotation of the airmotor 62, causing the air motor 62 and thus the socket 70 to rotate inthe reverse rotation at a low speed.

As previously described, the solenoid operated selector valve 95controls action of the hand 32, while the solenoid operated selectorvalves 96, 97, and 100 control action of open end air wrench 61.

The nut tightening robot 51 and open end air wrench 61 are controlled bythe control unit 111 as shown in FIG. 8.

The control unit 111 comprises a central processor unit (CPU) 112, anarithmetic logic circuit (ALC), and an output circuit 114 including adigital analog converter, a signal input interface 115, a signal outputinterface 116, a pulse counter 117, a differential circuit 118, and adriver 119. The CPU 112 operates based on a control program stored in amemory and supplies the ALC 113 with output signals indicative of a pathof movement of the hand of the nut tightening robot 51 and a velocity ofthe movement. It generates an output signal which is supplied via theoutput interface 116 to the solenoid operated selector valves 96, 97 and100 for activating the open-end air wrench 61. It receives an outputsignal of the limit switch 89 via the signal input interface 115.

The ALC 113 calculates a target position of each of joints of the nuttightening robots 51 and a target velocity thereof in order for the handof the nut tightening robot 51 to move along the path of movement givenby the CPU 112 at the velocity given by the CPU 112. Via the digitalanalog conversion at the output circuit 114, the output signals of theALC 113 indicative of the target position and velocity of each of thejoints are supplied to the driver 119. The driver 119 activates motorsfor the joints of the nut tightening robot 51. An actual positionindicative signal indicative of the actual position of each of thejoints of the nut tightening robot 51 is fed via the differentiationcircuit 118 to the ALC 113. In order to decrease a difference betweenthe desired and actual position indicative signals, the ALC 113modulates the target actual indicative signal supplied via the outputcircuit 114 to the driver 119.. The output signal of the encoder 72mounted on the open-end air wrench 61 is supplied to the pulse counter117 where the number of pulses is counted. The output signal of thepulse counter 117 is supplied to the ALC 113. Based on this outputsignal of the pulse counter 117, the ALC 113 calculates an angle of nutafter the nut tightening operation has been completed. The result ofthis calculation is fed to the CPU 112.

The differentiation circuit 118 calculates the first derivative of theactual position indicative signal supplied thereto to give an actualvelocity of each of the joints of the nut tightening robot 51. Theoutput of the differentiation circuit 118 indicative of the actualvelocity is supplied to the driver 119.

The apparatus according to the present embodiment operates in accordancewith the control program as illustrated in FIG. 9 to assemble two curvedpipes 3 in manufacturing the power steering gear assemblies as shown inFIG. 11.

The execution of the control program shown in FIG. 9 is initiated uponreceipt of production instruction of the power steering gear assembly.At a step 121, it is confirmed whether the preparation for assembling ofthe curved pipes has been completed or not. What are checked at thisstep 121 are whether the work, i.e., the gear housing 1 integral withthe power cylinder 2, and whether the NC pipe bender 11 stays in thewaiting state where the chuck 13 of the NC pipe bender 11 stays in therest position. Then, the program proceeds to a step 122 if thepreparation has been completed.

At the step 122, in accordance with the specification of the powersteering gear assembly to be produced following the productioninstruction, appropriate control programs for the NC pipe bender 11,pipe set robot 31 and nut tightening robot 51 are selected and loaded.Specifically, the selection of the appropriate control programs is madein accordance with the length of the straight pipes 3, the curvature tobe given to the pipe during the bending process, and the appropriatepositions of the pipes 3 relative to the gear housing 1 integral withthe power cylinder 2.

Then, the execution of the control programs is initiated. At a step 123,the NC pipe bender 11 has the pipe loader 21 to select the appropriateone out of four kinds of different, in length, straight pipes andoperates to bend the straight pipe 3 supplied to the predeterminedcurved shape. In this bending process, the appropriate gear housing 1 isconnected to the corresponding power cylinder 2, the pipe set robot 31stays in its waiting position where it does not interfere with thebending process of the pipe 3, see step 124, and the nut tighteningrobot 51 stays in its waiting position where it does not interfere withthe pipe set robot 31 operating to set the pipe 3, see step 125.

Upon completion of the bending process, the pipe set robot 31 let itshand 32 move to hold the pipe 3 held by the chuck 13 of the NC pipebender 11, see a step 126. Subsequently, at steps 127 and 128, the chuck13 releases the pipe 3 and returns to the rest position. Then, the pipeset robot 31 moves the pipe 3 to a waiting position where it does notinterfere with the gear housing 1 with the poser cylinder 2 disposed onthe pallet 41.

When the pallet 41 has reached a predetermined position, the programproceeds to a step 130 where the pipe set robot 31 set the pipe 3 at apredetermined position where the flare nuts 3a of the pipe 3 abutagainst the ports of the gear housing 1 and the power cylinder on theparallel 4 with the central axes of the flare nuts 3a arranged inalignment with the central axes of the ports of the gear housing 1 andpower cylinder 2, respectively.

Thereafter, at steps 131 and 132, the nut tightening robot 51 tightenthe flare nut 3a on the power cylinder 2 side of the pipe 3 with theopen-end air wrench 61, and tighten its firmly with the torque wrench 81to the predetermined torque. The nut tightening and the subsequenttorque check are performed by executing the control program as shown inFIG. 10.

Referring to FIG. 10, at a step 141, with the socket 70 held in thecentral rest position where the opening 70d faces forwardly toward thepipe 3, the open end air wrench 61 moves toward a position about toreceive the nut 3a where the socket 70 receives therein the pipe 3adjacent the nut 3a disposed near the power cylinder 2. Then, at a step142, the air wrench 61 is caused to rotate at a low speed.

At the subsequent step 143, the open end air wrench 61 moves toward thepower cylinder 2 until the socket 70 has the flare nut 3a to receivetherein. Thereafter, at a step 144, the air wrench 61 starts rotating ata high speed. It keeps on rotating at the high speed for a predeterminedperiod of time. This causes the flare nut 3a advance toward the powercylinder 2 until the flare nut 3a has a flared end portion of the pipe 3interposed between it and the bottom wall of the port structure of thepower cylinder 2, see FIG. 11(b).

After this tightening operation, the open end air wrench 61 is caused tostep back from the power cylinder to disengage the socket 70 from theflare nut 3a at a step 146. The, at a step 147, the air wrench 70 isrotates in the reverse direction until the socket 70 takes the centralrest position where the opening 70a faces forwardly. During this reverserotation, the number of pulses generated by the rotary encoder 72 iscounted. Using this result, an angle of rotation in the reversedirection till the socket 70 takes the central rest position isdetermined, and thus the direction along which two spaced opposed sidesof the flare nut 3a extend upon completion of the tightening process isdetermined.

Then, the bracket 52 is rotated through 180 degrees and the torquewrench 81 is caused to advance toward the pipe 3 till a position aboutto receive the nut 3a where the head 83 of the torque wrench 81 receivethe pipe 3 therein at a position adjacent the nut 3a. During thismovement of the torque wrench toward the pipe 3, the angular position ofthe torque wrench 81 which is to take for the two opposed paralled sides83a of the head 83 align with the two opposed sides of the flare nut 3ais calculated based on the result of counting the number of pulsesgenerated by the encoder 72. Then, at a step 149, the position of thetorque wrench 81 is revised to the position determined by thecalculation.

Thereafter, at a step 150, the torque wrench 81 is caused to move towardthe power cylinder 2 until the head 83 receives the flare nut 3atherein. At a step 151, the torque wrench 81 is rotated about the pipe 3in the nut tightening direction, and if, at a step 152, it is determinedthat the output signal of the limit switch 89 is received and thus thepredetermined torque has been achieved, the program proceeds to a step153. At the step 153, the torque wrench 81 is caused to step back awayfrom the power cylinder 2 to disengage the head 83 from the flare nut3a.

After the tightening of and torque check of the flare nut 3a on thepower cylinder 2 side have been completed, the program proceeds to astep 133 where the partial tightening of the flare nut 3a on the gearhousing 5 side is carried out.

The partial tightening of the nut 3a is carried out in substantially thesame manner as illustrated by the steps 141 to 145 except that insteadof high speed rotation of the air wrench 61 at steps 144 and 145, theair wrench 61 is turned at a low speed for a relatively short period oftime. With this operation, the flare nut 3a is temporarily engaged withthe port on the gear housing 1. This is an effective measure not toimpart big stress on the pipe 3 that is held by the pipe set robot 31,thus preventing deformation of the pipe 3. The program then proceeds toa step 134, the pipe set robot 31 is caused to release the pipe 3. Afterit is confirmed that the pipe set robot 31 has release the pipe 3, theprogram proceeds to steps 135 and 136 where the tightening of the flarenut 3a on the gear housing 1 side and the torque check are carried outin the same manner as illustrated in the flow chart in FIG. 10.

After releasing the pipe 3, the pipe set robot 31 returns to an intialrest position, see step 137. After the torque check at the step 136, thenut tightening robot 51 returns to its initial rest position, see step138.

While the pipe set robot 31 sets the pipe 3 and the nut tightening robot51 operates to tighten the flare nuts 3a, the NC pipe bender 11 performsbeinding of the second pipe 3 repeating the steps 123 to 128 unless itis decided that the second pipe 3 has been subjected to the bendingprocess.

If, at a step 140, it is decided that the second pipe 3 is not yetassembled, the pipe set robot 31 and the nut tightening robot 51 arecaused to assemble the second pipe 3 to the gear housing 1 intergal withthe power cylinder 2 by repeating the steps 126 to 138.

The present invention may be applied to assembling of pipes 5 with abrake master cylinder 4 as shown in FIG. 12 or assembling of a controlrod with a carburetor.

From the preceding description, it will now be appreciated thataccording to the present invention a space for storing parts has beenminimized since what are needed to store are elongate straight memberslike straight pipes or rods before being subjected to bending process.Besides, human error in selecting and assembling an inappropriate memberhas been eliminated.

What is claimed is:
 1. An apparatus for assembling small numbers of alarge variety of different products, comprising:means for delivering awork piece to a predetermined position, said work piece havingconnection means on an exterior portion thereof for receiving andconnecting an end of an elongated member thereto; means for storing avariety of different straight elongated members, each of said elongatedmembers having opposed ends; means for selecting a predeterminedstraight elongated member out of said variety of different straightelongated members in accordance with a production instruction; means forbending said predetermined straight elongated member in accordance withthe production instruction to form a curved elongated member; means forreceiving said curved elongated member and holding the same in apredetermined position adjacent to the exterior portion of said workpiece; and means for connecting at least one end of said curvedelongated member to said connection means on the exterior portion ofsaid work piece, said means for externally attaching being unconnectedto and separate from said curved elongated member and said work piece.2. An apparatus for assembling small numbers of a large variety ofdifferent products according to claim 1, wherein said work piece isselected from the group consisting of power steering assemblies, mastercylinder assemblies and carburetors.
 3. An apparatus for assemblingsmall numbers of a large variety of different products according toclaim 1, wherein said connection means comprises a plurality ofconnection means and said means for attaching includes means forattaching each end of said curved elongated member to said connectionmeans of said work piece.
 4. An apparatus for assembling small numbersof a large variety of different products according to claim 1, whereinsaid elongated members are selected from the group consisting of pipesand rods.
 5. An apparatus for assembling small numbers of a largevariety of different products according to claim 4, wherein saidelongated members comprise pipes with flared ends.
 6. An apparatus forassembling small numbers of a large variety of different productsaccording to claim 1, wherein each of said elongated members includeconnectors at each end thereof and said means for attaching comprisesmeans for connecting at least one of said connectors of said curvedelongated member to said connection means of said work piece.
 7. Anapparatus for assembling small numbers of a large variety of differentproducts according to claim 6, wherein said elongated members comprisepipes having flared ends and said connectors and connection meanscomprise connectable threaded fittings.
 8. An apparatus for assemblingsmall numbers of a large variety of different products according toclaim 7, wherein said means for attaching comprises means for checkingthe torque of the threaded connection between said work piece and saidcurved elongated member.